All water on earth is not usable because

1. Nearly 97% of the Earth’s total water is in the form of oceans and seas. It is saline.

2. Another 2% water is in the form of ice caps and glaciers.

3. Only 1% is fresh water available for human use. It is present in;

• In the form of ground water.
• In the formed surface water in rivers and lacks.
• In the atmosphere in the form of water vapour.